a) Field of the Invention
The present invention relates to a magnetic head of a hard disk drive or the like and its manufacture method. More particularly, the invention relates to a magnetoresistive type thin film magnetic head of a magnetic shield type and its manufacture method capable of lowering the resistance of a lead to suppress heat generation and prevent insufficient insulation of an upper magnetic shield layer to thereby improve manufacture yield. A magnetoresistive type thin film magnetic head is hereinafter called an "MR type magnetic head" and includes a giant magnetoresistive (GMR) type thin film magnetic head.
b) Description of the Related Art
An MR type magnetic head is used for only reproduction of information recorded in a magnetic recording medium by detecting a magnetic field generated from magnetic poles of a magnetic recording medium. As compared to reproduction by an induction type magnetic head, the track density and a line record density can be made higher. An induction type magnetic head for recording is combined with an MR type magnetic head to form an induction type and magnetoresistive type composite magnetic head (hereinafter called an "induction type and MR type composite magnetic head").
FIG. 2 shows the structure of an MR type magnetic head (with an upper reproduction gap layer and an upper magnetic shield layer being removed) of a conventional induction type and MR type composite magnetic head used for hard disks. An MR magnetic head 10 is formed on a slider substrate 12 made of Al.sub.2 O.sub.3 --TiC or the like by sequentially laminating a protective layer 14 made of non-magnetic insulating material such as Al.sub.2 O.sub.3, a lower magnetic shield layer 16 made of soft magnetic material such as NiFe alloy, and a lower reproduction gap layer 18 made of non-magnetic insulating material such as Al.sub.2 O.sub.3. On the reproduction gap layer 18, right and left leads (electrodes) 20, 20 are formed. An MR element 11 is connected between the leads 20, 20. The tip surface of the MR element 22 forms a recording medium facing surface (ABS: air bearing surface). The MR element 22 is made of a lamination of an MR film, a spacer, a transverse bias film, and the like. Each lead 20 is made of a lamination of a magnetic material layer (magnet layer) 26 for enhancing uniaxial anisotropy of the MR film to suppress Barkhausen noises (longitudinal bias layer) and an electrically conductive film 28 for lowering the electrical resistance of the lead 20.
In the structure shown in FIG. 2, the tip surface or ABS of the lead requires some mechanical strength and corrosion resistance because it is subject to a lapping process. Generally, the magnet film 26 is made of Co-containing alloy, and the electrically conductive film 28 is made of Ta or the like. These lead materials have a relatively high resistivity so that when a sense current flows through the MR element 22, heat generation becomes large and electromigration may be accelerated which is one cause of lowering the reliability of the magnetic head and considerably shortening the lifetime thereof. Electromigration is a phenomenon in which when a sense current flows at a high temperature, metal atoms are liberated and moved to increase the resistance of the leads.
In order to lower the resistance of leads, another structure has been proposed as shown in FIG. 3. In this structure, contact leads 30, 30 made of the same materials as the leads shown in FIG. 2 are formed only at regions near the ABS 24. Relatively thick main bulk electrodes 32, 32 made of material having a relatively low resistivity are formed in contact with and at the back of the contact leads along the depth direction of the MR element. Leads 34, 34 are constituted of these contact leads 30, 30 and main leads 32, 32.
An MR type magnetic head of a magnetic shield type (a magnetic shield type MR head) has an upper reproduction gap layer covering the MR element and leads, this gap layer being made of non-magnetic material such as A1.sub.2 O.sub.3. On this upper reproduction gap layer, an upper magnetic shield layer is formed being made of conductive and magnetic shield material. The upper magnetic shield layer is made of soft magnetic material such as NiFe alloy same as the lower magnetic shield layer. With the structure shown in FIG. 3, a large step 36 is formed on the lead 34 so that the upper reproduction gap layer cannot be formed to have a predetermined thickness at this step 36. It is therefore difficult to provide perfect electrical insulation between the lead 34 and the upper magnetic shield layer, and manufacture yield is caused to be lowered.